With the arrival of summer temperatures, producers are reminded that water plays an essential role in a healthy calf including rumen development. Healthy calves under heat stress will drink between 6 and 12 quarts of water daily just to maintain normal hydration. Severely sick calves under heat stress sometimes require up to 20 quarts replacing what has been lost. According to the National Dairy FARM program Animal Care Manual Version 3.0 (2016), best practice is to provide calves access to clean, fresh water from the first day of life. However, according to the National Dairy Health Monitoring System (USDA, 2014), the average age of heifers when first offered water in the United States is 17.3 days.
One very important role that water plays is in rumen development. When a calf drinks water, the water goes into the rumen, as does the starter feed. Milk, fed from bottle or bucket, by-passes the rumen via esophageal groove, and is deposited into the abomasum of the calf. Water in the rumen provides a medium for ruminal bacteria to live in. To ferment grain and hay, rumen bacteria must live in water. Without water ruminal development is slowed. Thus, milk or water added to milk will not provide water for the bacteria to grow in the calf’s rumen
A 1984 landmark study examined the growth, health and starter intake of calves fed free choice water, or no water throughout the milk feeding period and found that when no fresh water was offered, starter intake was 31 percent less and weight gain was reduced by 38 percent.
High total solids in milk or milk replacer can create a situation where the osmotic balance in the calf is out of equilibrium and water is pulled out of cells resulting in diarrhea and dehydration, even in a calf drinking plenty of milk. Providing fresh water will allow the calf to self-adjust to some degree, lessening the severity of dehydration.
A study in 2011 found that water consumption of pre-weaned calves was higher in calves offered warm water compared to those offered cold water. However, the increased water intake of the calves offered warm water did not equate to increased weight gains. It is worth considering starting baby calves on warm water to encourage water consumption, especially during cooler weather: However, drinking water temperature above 86°F may reduce consumption.
Another factor on water for calves is to ensure the quality of the water. Extension professionals recommend periodically testing water sources for bacteria and mineral content. Calves are very sensitive to sodium and do not tolerate excess sodium well. Water that has passed through a water softener can have very high concentrations of sodium and should not be used to mix milk replacer or used as a source of drinking water unless it has been tested and verified to have levels of sodium below 100 ppm.
Several factors should be evaluated if problems with the drinking water supply are a suspicion. Abnormally high concentrations of sulfate and chloride are often of concern. In general sulfate recommendations are less than 500 ppm for calves and the Iowa water quality standard for chloride is 250 mg/L for drinking water. In addition, total bacteria counts in excess of 500 per 100 milliliters may indicate water-quality problems. Water sources with total bacteria counts in excess of 1 million per 100 milliliters should be avoided for all livestock classes.
In addition, keep water buckets free from environmental contamination including dirt, feed, manure and algae. Researchers out of Utah State University found increased daily gains and weaning weights when water buckets were dumped and rinsed daily compared to weekly or every 14 days. It is helpful to have a divider between the water and starter buckets in the calf pen so that the calf cannot slop back and forth between buckets.
More information on calf health and water quality is available on the ISUEO Dairy Team website: http://www.extension.iastate.edu/dairyteam